ES2879898T3 - Device to lighten the weight of crankshafts - Google Patents

Abstract

The device for lightening the weight of vehicle components comprises a tool (10) provided with a footprint (11) where the component is formed and a plurality of movable bodies (1a, 1b), which are movable between an initial position and a final position. final, so that in the final position one end of each movable body (1a, 1b) penetrates the tread (11) of the tooling to form a cavity to lighten the weight in a vehicle component (10), in which at least one of said movable bodies (1b) is laterally movable. It allows lightening the weight in a simpler and more productive way than in currently known systems. This is achieved because the movable bodies do not interfere with each other during their movement, so that the lightening process can be carried out in a one-shot forging process.

Description

DESCRIPTION

Device to lighten the weight of crankshafts

The present invention relates to a device for calibrating and lightening the weight of crankshafts of a vehicle engine.

Background of the invention

Over the past decades, automobile and automotive component manufacturers have been forced to adhere to increasingly stringent environmental restrictions when developing their products. Pressure, both from society and from governments to improve energy efficiency and vehicle emission levels is a factor that has an immense impact on the sector.

On the other hand, there is enormous pressure within the automotive sector to reduce costs, which implies taking action at all stages of the value chain of a product.

The key factor to meet this challenge is weight reduction: the smaller a vehicle is, the less power it requires to accelerate it, and the less energy it requires to maintain a constant speed, in addition to a lower cost of raw materials for the manufacturer of the product.

The new internal combustion engines must have a lot of power, little fuel consumption, a small size and must be, as far as possible, harmless to the environment. For example, crankshafts have a significant influence on engine performance as they are the component responsible for power generation, so their strength-to-weight ratio is essential.

Among the metal forming procedures, forging is considered the most suitable for the manufacture of crankshafts. In general, stamping at high forging temperatures is the procedure that gives the best results. This process is capable of producing high quality components at a moderate cost. Forging offers a high degree of strength in relation to weight, toughness, and resistance to fatigue and impact, important factors in crankshaft design and performance.

To define the forging procedure, first of all, it is necessary to size the block of material to be forged. To size the block, it is necessary to define the load factor, which corresponds to a coefficient by which the volume of the part must be multiplied to avoid material losses in the burr. Once this factor has been determined, a previous dimensioning of the block is carried out.

In addition, it is necessary to know in how many strokes the part will be forged. To do this, a rule is used to define whether to use one stroke (final form), two strokes (previous and final form), three strokes (two previous forms and one final form), or four strokes (three previous forms and one final form). final).

A method for manufacturing a crankshaft is known from US 2014/0318310 A1. This document describes a procedure for lightening crankshafts during the forging process without degrading the strength of the crankshaft.

The case mentioned in this document consists of a crankshaft, with a cavity formed in each module of the crankshaft on the side where the crank pins are located. These cavities are formed by a series of movable bodies that penetrate the tool's footprint during a forging process. This is because that part is usually chamfered and, in this way, the access of the movable bodies that produce the cavities is easier than in a plane that is perpendicular to the axis of rotation of the crankshaft.

In addition, the fact that this is one of the areas of the piece with the greatest accumulation of material makes it the optimal part to make cavities, since removing material there will have a lesser impact on the rigidity of the piece than in other areas. of the same, in which the stiffness would be degraded to a greater extent.

The procedure described in this document discusses the problem for a 4-cylinder, 8-counterweight flat crankshaft. The movable bodies take advantage of the inclination of the outer areas of the chamfers in which the crank pins are located to penetrate the part in a practically perpendicular way, something that in another area of the crankshaft would be impossible due to space problems in the tooling.

This document proposes a solution in which there are two types of cavities in the crankshaft. The first presents a greater contact area and a smaller depth of penetration in the crankshaft, while the second is the opposite case, the contact surface is smaller with a greater depth in the crankshaft.

With this solution it is achieved that the two movable bodies that penetrate the crankshaft at each journal have the same inclination with respect to the median plane of the cross section of the journal.

The reason for this difference in geometry between the two cavities is the following: a very fine separation can be observed between the two voids in relation to the size of the cavities to be made. It's about a oil passage conduit that is part of the engine unit cooling circuit. Oil passes from the shaft through one hole to the crankpin surface through another hole.

The main problem with making both cavities with the same geometry is that at least one of the two would invade the space occupied by the oil duct, a fact that should not occur.

Two chamfers are joined by their corresponding journal before the movable bodies penetrate the part to form the cavities. The two chamfers go from being at a distance A (equal to the length of the crankpin) to being at a practically zero distance B which, apart from structural problems, would prevent the correct rotation and operation of the crankshaft.

In a graphical representation of the level of lateral deformation of the counterweights, it can be seen how the displacement presents a linear relationship with respect to the level of clearance between the preform and the tooling up to 0.5 mm, and a relationship with a slope approximately 4 times greater than starting from 0.5 mm, making it a highly relevant factor.

On the other hand, to carry out a procedure such as that described in this document, it is necessary to follow a specific order in the formation of the cavities, so that the movable bodies to be penetrated do not collide with each other during the procedure.

Therefore, the procedure and the device described in this document have the problem of interference between the movable bodies if the procedure is to be carried out in one stroke.

Consequently, the objective of the present invention is to provide a method and a device for calibrating and lightening the weight of automobile components with a higher productivity than with currently known methods and devices.

Description of the invention

With the method and device of the invention it is possible to solve the aforementioned drawbacks, presenting other advantages that will be described below.

The device for calibrating and lightening the weight of a crankshaft according to the present invention is defined in claim 1.

Advantageously, at least one or all of the movable bodies comprise a recessed portion near said end that forms the cavity to lighten the weight, said recessed portion defining a projecting portion at said end, said projecting portion forming said cavity, moving the bodies diagonally to the tooling footprint.

Advantageously, said projecting portion and said recessed portion have rounded edges.

According to two alternative embodiments, said projecting portion may have a substantially semicircular shape in a plan view, or said projecting portion may have a substantially rectangular shape with its minor sides curved in a plan view, depending on the type of body. scrollable.

Advantageously, a type of movable bodies, which are mounted on said intermediate piece, comprise respective bevels, said movable bodies being substantially in contact with each other through these bevels, and furthermore the bevel of each movable body is arranged at the end provided with said projecting portion.

According to a preferred embodiment, said tooling comprises a lower edge piece on which the movable bodies are mounted and an upper edge piece, said upper edge piece being movable with respect to said lower edge piece and the set of said Lower and upper edge pieces movable relative to a frame of the device.

Furthermore, said wedges are advantageously fixedly mounted on the frame of the device, so that the movement of the assembly of said upper and lower edge pieces causes the displacement of the movable bodies from their initial position to their final position.

To return to its initial position, each movable body is advantageously associated with a spring, which presses the movable body back to its initial position.

With the device according to the present invention, a component for vehicles with a lighter weight is achieved, being able to lighten and calibrate the weight in a simpler and more productive way than in the systems known today.

This is achieved with the device according to the present invention because the movable bodies do not interfere with each other during their movement, so that the calibration and lightening procedure can be carried out in a one-shot forging procedure.

Brief description of the drawings

In order to help better understand the following description, it is accompanied by a group of drawings that, schematically and by way of illustration and not limiting, represent one embodiment.

Figure 1 is a schematic perspective view of the device for calibrating and lightening the weight of crankshafts according to the present invention;

Figures 2 and 3 are perspective views of two types of movable bodies that are used in the device to calibrate and lighten the weight of crankshafts according to the present invention;

Figure 4 is a schematic plan view of a crankshaft indicating the initial position of the movable bodies of the device for calibrating and lightening the weight of crankshafts according to the present invention; and Figure 5 is a schematic plan view of a crankshaft indicating the final position of the movable bodies of the device for calibrating and lightening the weight of crankshafts according to the present invention.

Description of a preferred embodiment

First of all, it should be noted that this preferred embodiment is described in relation to a crankshaft for a motor vehicle.

As indicated above, in a crankshaft it is advantageous to remove material in the chamfers adjacent to each crankpin. This is because they are low-demand areas at the voltage level, which do not have any type of functionality.

The device according to the present invention comprises a tooling 10, formed by a lower edge piece 12 and an upper edge piece (not shown in the figures), as will be described later. Said tooling 10 defines a footprint 11, in the shape of the component to be manufactured, such as a crankshaft 14.

For the formation of cavities in the component, the device according to the present invention comprises a plurality of movable bodies 1a, 1b, which can move between an initial position (figure 4) in which said movable bodies 1a, 1b are outside of said footprint 11, and a final position (figure 5) in which one of the ends of each movable body 1a, 1b is inside the footprint 11 to form said cavities when component 14 is manufactured.

In the case of crankshafts, component 14 has two types of chamfers. For this reason, it is necessary to design two types of cavities, adapting them to the shape of each chamfer and, therefore, the device according to the present invention will comprise two types of movable bodies, identified respectively by the references 1a and 1b, it is that is, first movable bodies 1a and second movable bodies 1b.

Said first movable bodies 1a can be displaced longitudinally along their longitudinal axis and said second movable bodies 1b can be displaced laterally, that is to say perpendicular to their longitudinal axis.

Figures 2 and 3 show a first movable body 1a and a second movable body 1b, respectively.

In both cases, the movable body 1a, 1b comprises a recessed portion 2 near one end of the body. This recessed portion 2 defines a projecting portion 3, which is what forms the cavity in the component 14.

As can be seen in figure 2, in the case of the first movable body 1a, said projecting portion 3 has a substantially rectangular plan shape with its curved minor sides, while, in the case of the second movable body 1b, the projecting portion 3 has a substantially semicircular plan shape. In addition, in both cases the edges are rounded, to avoid sharp edges.

In the case of the first movable bodies 1a, these are positioned as shown in the figures. The first movable bodies 1a are mounted on wedges 4 for the diagonal movement of the first movable bodies 1a, as will be described below. For this, the first movable bodies 1a comprise an inclined surface 6 that is in contact with the wedge 4.

For their part, according to the embodiment shown, two second movable bodies 1b are placed in a centered position as seen in the figures. These second movable bodies 1b are mounted on an intermediate piece 5, which in turn is mounted on a wedge 4. In the initial position (figure 4), said second movable bodies 1b are substantially in contact with each other by means of a chamfer 7, while which in the final position (figure 5) are separated.

The assembly of the device according to the present invention is carried out in the following way. First, the assembly of a lower edge piece 12 for calibration is carried out.

Next, springs 15 are mounted that return the movable bodies 1a, 1b to their initial position. Next, the movable bodies 1a, 1b and the intermediate piece 5 are mounted in position.

Subsequently, fasteners of the lower edge piece 12 and a nose plate 17 are mounted, which serves to provide rigidity to the assembly. Finally, the assembly is placed on a frame 16 with the wedges 4 integrated.

The calibration procedure, which is the one carried out by means of the device according to the present invention, is the last operation in the crankshaft manufacturing procedure. It should be noted that before this calibration procedure, during which the weight of the crankshaft is lightened, other steps are carried out, which are not described in the present description because they are obvious to the person skilled in the art and do not form part of the present invention. .

The procedure for calibrating and lightening the weight of the component is as follows.

First, the upper edge piece lowers until it makes contact with the lower edge piece 12 (which until that moment was immobile) and closes the device, enclosing the component 14. From that point, both edge pieces are move down jointly as a single block.

This block movement is possible thanks to the fact that the lower edge piece 12 is placed on a group of cylinders (not represented in the figures), which act as a spring, and allow this effect.

The lower edge piece 12 carries the movable bodies, which penetrate the chamfers of the crankshaft mentioned above, forming the cavities, secured with the springs.

The movement of these movable bodies can be divided into two parts:

- Movement with respect to the tooling: the springs that hold the movable bodies to the tooling and restrict its movement with respect to the XY plane (considering that the set of the upper and lower edge part moves in the Z axis).

- Movement with respect to the absolute coordinate axis: during the movement of the assembly, each movable body slides on a wedge 4 that is immobile. These wedges 4 make the movable bodies 1a, 1b move diagonally. The vertical component of that movement is equal to the movement of the edge pieces, and the horizontal component of the movement is equal to the movement with respect to the tooling.

When the cavities have been formed, the cylinders return the set of edge pieces to their initial position. The springs 15 that hold the movable bodies 1a, 1b also return them to their initial position.

Despite the fact that reference has been made to a specific embodiment of the invention, it is clear to a person skilled in the art that the device described is susceptible to numerous variations and modifications, and that all the mentioned details can be replaced by other technically equivalent ones, without departing from the scope of protection defined by the appended claims.

Claims (12)

1. A device for calibrating and lightening the weight of crankshafts, comprising a tooling (10) provided with a footprint (11) for the crankshaft; a plurality of movable bodies (1a, 1b), which can move between an initial position and an end position, so that, in the final position, one end of each movable body (1a, 1b) penetrates the footprint (11) to form a cavity to lighten the weight of the crankshaft; and wedges (4), on which the movable bodies (1a, 1b) are mounted, provided with an inclined plane Z to move the bodies (1a, 1b) with respect to the footprint (11) of the tooling (10), characterized because two of said bodies (1b) are mounted on an intermediate piece (5) which, in turn, is mounted on one of said wedges (4) so that said movable bodies (1b) can be laterally displaced to their respective longitudinal axis . The device for calibrating and lightening the weight of crankshafts according to claim 1, wherein at least one or all of the movable bodies (1a, 1b) comprise a recessed portion (2) near said end forming the cavity to lighten the weight, said recessed portion (2) defining a protruding portion (3) at said end, said protruding portion (3) forming said cavity. The device for calibrating and lightening the weight of crankshafts according to claim 1, wherein at least one or all of the movable bodies (1a, 1b) comprise (n) an inclined surface (6) complementary to the inclined plane of said wedges (4). The device for calibrating and lightening the weight of crankshafts according to claim 2, wherein said projecting portion (3) has rounded edges. The device for calibrating and lightening the weight of crankshafts according to claim 2, wherein said recessed portion (2) has rounded edges. The device for calibrating and lightening the weight of crankshafts according to claim 2, wherein said projecting portion (3) has a substantially semicircular shape in a plan view. The device for calibrating and lightening the weight of crankshafts according to claim 2, wherein said projecting portion (3) has a substantially rectangular shape with its minor sides curved in a plan view. The device for calibrating and lightening the weight of crankshafts according to claim 1, wherein the movable bodies (1b) mounted on said intermediate piece (5) comprise respective bevels (7), said movable bodies (1b) being substantially in contact with each other through these bezels (7). The device for calibrating and lightening the weight of crankshafts according to claim 8, wherein the chamfer (7) is arranged at the end provided with said projecting portion (3). The device for calibrating and lightening the weight of crankshafts according to claim 1, wherein said tooling (10) comprises a lower edge piece (12) on which the movable bodies (1a, 1b) and an upper edge piece, said upper edge piece being able to move with respect to said lower edge piece (12) and the assembly of said lower edge pieces (12) and upper edge being able to move with respect to a frame (16) of the device . The device for calibrating and lightening the weight of crankshafts according to claims 1 and 10, wherein said wedges (4) are advantageously mounted in a fixed manner on the frame (16) of the device, so that the movement of the The assembly of said lower (12) and upper edge pieces causes the displacement of the movable bodies (1a, 1b) from their initial position to their final position. The device for calibrating and lightening the weight of crankshafts according to claim 1, in which each movable body (1a, 1b) is associated with a spring (15), which presses the movable body (1a, 1b) of back to its starting position.